A speaker is an acoustic part for completing the conversion between an electrical signal and a sound signal and is an energy conversion device. The speaker includes a housing within which a vibration system and a magnetic system is contained. The vibration system includes a folding ring, a connector, a dome, a skeleton voice coil and a damper combined together, and the magnetic system includes a washer, a magnet and a magnetic permeability piece combined together. A magnetic gap is provided between the washer and the magnet and a magnetic permeability piece. The end portion of the skeleton voice coil with windings winded is located within the magnetic gap. The skeleton voice coil makes up and down movement within the magnetic gap according to the acoustic electrical signal passing through the windings thereof. An induced electromotive force will be generated while the skeleton voice coil makes up and down movement in the magnetic field. A modulated magnetic field will be generated by the current of the sonic signal and the induced electromotive force. An eddy current will be generated in the washer, the magnet and the magnetic permeability piece by the modulated magnetic field, which reduces the energy of the magnetic field and at the same time cause the second harmonic distortion of the speaker, thus affecting the acoustic performance of the speaker.
The current main method for solving the above-said problem is to mount a short circuit ring in the speaker. Though the short circuit ring eliminates the above defect, it increases the internal components of the speaker, which increases the production cost, at the same time also increases the complexity and difficulty of the assembling of the speaker, increases the probability of bad assembling and reduces the production efficiency and the qualified rate of the end product of the speaker.